The development and appropriate use of experimental in vivo models of bladder cancer were given a high priority in the overall research program developed for the National Bladder Cancer Project. Such models are badly needed for studies on the detection, diagnosis and treatment of this disease. For many studies of tumor-host relationships in general, and tumor immunology in particular, the use of inbred strains of laboratory animals would be almost imperative. We propose to characterize the experimental model of bladder cancer in the inbred Fischer rat following tumor induction by the oral administration of the carcinogen N-(4-(5-Nitro-2-furyl)-2-thiazolyl) formamide, otherwise known as FANFT. We propose to study particularly the reproducibility of the model, the reversibility of the mucosal lesions after varying periods of carcinogen feeding, and the possible presence of two stages (initiation and promotion) in the pathogenesis of these epithelial tumors. These aspects of the model relate to "early" stages in the pathogenesis of human bladder cancer. We intend to study patterns of spread of the primary tumors and the relationship of local extension and distant metastases to the cause of death of these animals in an effort to determine if this tumor-host system would be a useful model for late stages of the human disease. In addition, while we are working with induced primary tumors, we propose to develop serially transplantable lines of bladder tumors in Fischer rats for possible use by us or by others in investigations of immuno-diagnostic or immunotherapeutic procedures, or of tumor-host interactions.